1. Technical Field
This invention relates to heat exchangers for refrigeration circuits, and more particularly, to an evaporator for an automotive air conditioning refrigeration circuit.
2. Description Of The Prior Art
Evaporators for use in automotive air conditioning refrigeration circuits are known in the art. With reference to FIG. 1, a serpentine type evaporator or heat exchanger 10 is shown. Evaporator 10 includes a continuous serpentine flat tube 11 through which refrigerant fluid flows. Serpentine tube 11 includes a plurality of spaced parallel planar portions 12 and a corresponding plurality of bent portions 121. Air flows through evaporator 10 between planar portions 12 in the direction of the arrow shown in FIG. 1. As shown in FIG. 2, the interior space of serpentine tube 11 is divided by a plurality of parallel partition walls 111 into a corresponding plurality of essentially parallel passages through which refrigerant fluid flows. One terminal end of serpentine tube 11 is brazed to fluid inlet header pipe 17 which is connected to an inlet pipe 15. The opposite end of inlet pipe 15 is connected to an expansion means (not shown) of a refrigeration circuit. A second terminal end of serpentine tube 11 is brazed to fluid outlet pipe 16. Outlet pipe 16 is connected to a compressor which provides suction for causing the refrigerant fluid to flow through the circuit. Refrigerant fluid is supplied to serpentine tube 11 from the expansion means via inlet pipe 15, flows through each successive planar portion 12 and bent portion 121 towards outlet pipe 16, and is then returned to the compressor. Of course, the refrigeration circuit may include other elements disposed between the compressor and evaporator 10.
Evaporator 10 further includes corrugated heat receiving metal sheets or fin units 13 disposed between opposed planar portions 12. Fin units 13 are fixed to planar portions 12 by brazing along the lines of contact. Protective side plates 14 are fixed to the exterior side of each of the outside fin units 13.
As seen from the evaporator shown in FIG. 1, the inlet pipe 15 extends form the front side to the rear side of the evaporator and then joins to the header pipe 17 at its back end. This kind of u-shaped inlet tube bending is called a return-bend. This piping structure provides a so-called counter flow between the refrigerant fluid flow and an air flow so that an effective heat transfer can be obtained in the evaporator.
There is another prior art evaporator shown in FIG. 3 which is a so called fin and tube evaporator 30. Evaporator 30 includes an inlet pipe 31, and outlet pipe 32, fins 33 and connection tubes 34 which extends between U-shaped pipes 35. The refrigerant fluid flows from the inlet pipe 31 through tubes 34 and the U-shaped pipes 35 and into the outlet pipe 32. As compared with evaporator 10 shown in FIG. 1, the inlet pipe 31 and the outlet pipe 32 shown in FIG. 3 are connected to the evaporator 30 along one side. In this construction no space is taken in the front or rear of the evaporator. This space factor is an advantage of the fin and tube evaporator over a serpentine type evaporator. Due to this difference in inlet and outlet connections, difficulty has been encountered in installing a serpentine type evaporator into an air conditioner cooling case originally designed to accommodate a fin and tube evaporator.